//===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file provides a template class that determines if a type is a class or
// not. The basic mechanism, based on using the pointer to member function of
// a zero argument to a function was "boosted" from the boost type_traits
// library. See http://www.boost.org/ for all the gory details.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_TYPE_TRAITS_H
#define LLVM_SUPPORT_TYPE_TRAITS_H

#include <utility>

// This is actually the conforming implementation which works with abstract
// classes.  However, enough compilers have trouble with it that most will use
// the one in boost/type_traits/object_traits.hpp. This implementation actually
// works with VC7.0, but other interactions seem to fail when we use it.

namespace llvm {

namespace dont_use {
// These two functions should never be used. They are helpers to
// the is_class template below. They cannot be located inside
// is_class because doing so causes at least GCC to think that
// the value of the "value" enumerator is not constant. Placing
// them out here (for some strange reason) allows the sizeof
// operator against them to magically be constant. This is
// important to make the is_class<T>::value idiom zero cost. it
// evaluates to a constant 1 or 0 depending on whether the
// parameter T is a class or not (respectively).
template <typename T>
char is_class_helper(void (T::*)());
template <typename T>
double is_class_helper(...);
} // namespace dont_use

template <typename T>
struct is_class {
  // is_class<> metafunction due to Paul Mensonides (leavings@attbi.com). For
  // more details:
  // http://groups.google.com/groups?hl=en&selm=000001c1cc83%24e154d5e0%247772e50c%40c161550a&rnum=1
public:
  enum { value = sizeof(char) == sizeof(dont_use::is_class_helper<T>(0)) };
};

/// isPodLike - This is a type trait that is used to determine whether a given
/// type can be copied around with memcpy instead of running ctors etc.
template <typename T>
struct isPodLike {
  // If we don't know anything else, we can (at least) assume that all non-class
  // types are PODs.
  static const bool value = !is_class<T>::value;
};

// std::pair's are pod-like if their elements are.
template <typename T, typename U>
struct isPodLike<std::pair<T, U>> {
  static const bool value = isPodLike<T>::value & isPodLike<U>::value;
};

/// \brief Metafunction that determines whether the two given types are
/// equivalent.
template <typename T, typename U>
struct is_same {
  static const bool value = false;
};

template <typename T>
struct is_same<T, T> {
  static const bool value = true;
};

// enable_if_c - Enable/disable a template based on a metafunction
template <bool Cond, typename T = void>
struct enable_if_c {
  typedef T type;
};

template <typename T>
struct enable_if_c<false, T> {};

// enable_if - Enable/disable a template based on a metafunction
template <typename Cond, typename T = void>
struct enable_if : public enable_if_c<Cond::value, T> {};

namespace dont_use {
template <typename Base>
char base_of_helper(const volatile Base*);
template <typename Base>
double base_of_helper(...);
} // namespace dont_use

/// is_base_of - Metafunction to determine whether one type is a base class of
/// (or identical to) another type.
template <typename Base, typename Derived>
struct is_base_of {
  static const bool value =
      is_class<Base>::value && is_class<Derived>::value &&
      sizeof(char) == sizeof(dont_use::base_of_helper<Base>((Derived*)0));
};

// remove_pointer - Metafunction to turn Foo* into Foo.  Defined in
// C++0x [meta.trans.ptr].
template <typename T>
struct remove_pointer {
  typedef T type;
};
template <typename T>
struct remove_pointer<T*> {
  typedef T type;
};
template <typename T>
struct remove_pointer<T* const> {
  typedef T type;
};
template <typename T>
struct remove_pointer<T* volatile> {
  typedef T type;
};
template <typename T>
struct remove_pointer<T* const volatile> {
  typedef T type;
};

template <bool, typename T, typename F>
struct conditional {
  typedef T type;
};

template <typename T, typename F>
struct conditional<false, T, F> {
  typedef F type;
};

} // namespace llvm

#endif
